This invention relates to an improved radiator assembly for supporting a cooling core of a radiator. A cooling core is typically formed of tubes, either flat or round, that span between a pair of header plates wherein the opposite ends of the tubes are bonded. The cooling core must be supported within side frames and the side frames need to be arranged so as to allow expansion and contraction of the core. It is therefore a basic object of this invention to provide an improved radiator assembly formed of a core and a frame for holding the core which allows the core to contract and expand within the frame.